The chemistry of trace metals and oxygen have significant implications in such health related areas as cancer chemotherapy and heart and lung disease. The importance of oxygen binding to various types of heme units in biological molecules is well known especially in regard to 02 transport and the respiratory process. The interaction of manganese with 02 is postulated in such reactions as photosynthetic 02 evolution in chloroplasts and the scavanging of superoxide ion, a radical anion, by superoxide dismutase. Being a trace metal in rather fragile systems creates experimental problems regarding the role and nature of manganese. A detailed investigation into the interaction of oxygen with relatively simple manganese coordination compounds is proposed. The research program envisioned is fivefold: (1) preparation and characterization of potential manganese-dioxygen precursors employing a range of polydentate ligands, (2) synthesize and study the oxygenation products of manganese(II) chelates, (3) measure core orbital ionization energies of manganese and oxygen in oxygenation products and precursors via X-ray photoelectron spectroscopy, (4) measure valence ionization energies of manganese(II) complexes via mass spectrometry and (5) study the redox properties of manganese compounds as a function of donor atom. Factors to be elucidated include the structural requirements for reversible 02 uptake, the nature of the Manganese- oxygen linkage and the role of manganese in photosynthetic 02 evolution and superoxide dismutase.